Method and apparatus for reducing ozone output from ion wind devices

ABSTRACT

Ozone output in ion wind devices using one or more emitters (10) and an array of collectors (20) (accelerators) may be reduced through catalytic conversion of the produced ozone back to oxygen by using various materials placed in or downstream from the airflow, such as a manganese dioxide coating on the accelerator substrate elements. Precious metal or activated carbon coatings may also be used for the purpose of converting ozone to oxygen.

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] This invention relates generally to ion generators and ion winddevices, and more specifically to an improved method and apparatus forreducing the ozone output from ion wind devices.

[0003] 2. Background Art

[0004] Ion wind devices such as described in Lee U.S. Pat. No. 4,789,801provide accelerated gas ions through the use of differential highvoltage electric fields between one or more emitters and an array ofcollectors (accelerators). The ions are entrained in the ambient bulkgases, causing the gases to flow. Gas velocities can reach as high aseight hundred feet per minute. However, the high voltage electric fieldsused to generate the gas ions and provide the force necessary for gasacceleration are also responsible for creating molecular dissociationreactions, the most common of which include ozone generated from oxygenwhen such devices are operating in a breathable atmosphere. It is anobject of this invention to provide methods to reduce the ozone outputby converting the produced ozone back to oxygen.

[0005] The U.S. Food and Drug Administration has determined that indoorairborne ozone in concentrations above 50 ppb (parts per billion) may behazardous to humans. NIOSH has ruled that indoor concentrations of ozoneabove 100 ppb may be hazardous to humans. Devices which utilize highvoltage electric fields to generate atmospheric plasma, corona dischargeand air ions are all susceptible to generating the allotrope, ozone.There exist a linear relationship between the level of the high voltagefields and current and the level of ozone concentration in most directcurrent operated ion wind systems. Also, a linear relationship existsbetween the acceleration velocity and intensity of the electric fields(typically the higher the voltage the higher the acceleration). Since itis desired to have maximum acceleration, methods must be employed tolimit or eliminate unwanted ozone output.

DISCLOSURE OF INVENTION

[0006] When ozone is produced in ion wind devices it may be convertedback to oxygen by using various materials placed in or downstream fromthe airflow. Noble metals such as gold, silver or platinum may be platedto the leading edge (or the entire surface) of the accelerator arraysubstrate to function as a catalytic converter to convert the ozone tooxygen. However, precious metal plating may not be a practical method ofcatalyzing ozone due to the high cost of the precious metal materialitself. Accordingly, the invention discloses a method to plate manganesedioxide onto accelerator substrate elements which also reduces, throughcatalytic conversion, ozone levels. The MnO₂ coating will catalyze ozoneto from O₂ (O₃-O₂) thus reducing ozone from the airflow. Activatedcarbon coatings may also be used for the purpose of converting ozone tooxygen.

[0007] The disclosed manganese plating and oxidation process has provensuccessful in reducing by greater than 20% the concentration of ozonedownstream from the primary emissivity source.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a schematic view of an emitter and accelerator array ofan ion wind device; and

[0009]FIG. 2 is a side elevation view of an apparatus for platingmanganese to an accelerator substrate.

BEST MODE FOR CARRYING OUT THE INVENTION

[0010]FIG. 1 is a schematic view of a typical ion wind array. Theemitter or emitters 10 are typically constructed of 0.1 mm pure tungstenwire and may be of any length. The collectors (also referred to asaccelerators) 20 are typically constructed of any non corrosiveconductive material such as copper, aluminum, stainless steel, or brass.The emitter 10 is always located opposite and at the center (A) of theopening of the accelerators 20. The equidistant (B) of the emitter tothe leading edge (radius) of the accelerators 20 may vary depending upondesired operational effect, but is typically one inch. This is also trueof the spacing (C) between accelerators.

[0011] The differential voltage applied across the array must be atleast 6,500 volts in order to effect any substantial ion mobility andsubsequent airflow. Typical configurations consist of applying apositive high voltage to the emitter and a negative high voltage to thecollector to achieve a maximum differential voltage of 15,000 volts D.C.These voltage potentials may be reversed, however, when this is done anuneven plasma envelope is developed at the emitter source, which resultsin excessive production of corona noise and ozone production. The arraymay be driven by a single positive or a single negative high voltageexcitation source to the emitter with the collectors having a highimpedance return to ground (to reduce load current and breakoverarcing). Also, the excitation voltage may be modulated in ways taught inU.S. Pat. No. 4,789,801 to achieve desired results.

[0012] FIG.2 is a side elevation view of an apparatus for platingmanganese to an accelerator substrate 20. Plating tank 30 is filled witha solution 32 of manganese sulfate, ammonium sulfate, and EDTA indistilled water, and mixed a with magnetic stirring plate 34 and spinbar 36. Bath heater 38 may be used to maintain the bath temperature at40 degrees C. Power supply 40 negative lead 42 is connected toaccelerator substrate 20, and positive lead 44 is connected to one ormore manganese plates or rods 46, and the substrate and manganese rodsare placed in the plating tank 30. The power supply is energized for anappropriate period to plate a desired layer of manganese onto thesubstrate 20. After the plating process, the manganese coating on thesubstrate is oxidized as by immersion in a hydrogen peroxide solution.

[0013] Procedural guidelines for the plating process may include thefollowing:

[0014]1.0 Purpose: Preparation of a plating bath for manganese, theplating of that metal onto a substrate, and the oxidation of the metalcoating.

[0015]2.0 Definitions

[0016]2.1 Substrate: Object which is to be plated.

[0017]3.0 Equipment and Supplies

[0018]3.1 Laboratory scale, triple beam balance (accuracy+/−0.05 gram).

[0019]3.2 Magnetic stirring plate.

[0020]3.3 Magnetic spin bar.

[0021]3.4 Plating tank, glass cylinder (approximately 5 inches indiameter and 13 inches long).

[0022]3.5 Plating bath heater (e.g., aquarium heater approximately 100watts).

[0023]3.6 Distilled water.

[0024]3.7 Manganese sulfate MnSO₄ 2H₂O.

[0025]3.8 Ammonium sulfate (NH₄)₂ SO₄

[0026]3.9 EDTA, disodium (ethylenediaminetetraacetate).

[0027]3.10 Manganese rods or plate (12 inches in length).

[0028]3.11 Electrical leads (3 feet in length with alligator clips 20watt minimum capacity).

[0029]3.12 Power supply (D.C. 0 to 20 watts capacity with currentmeter).

[0030]3.13 Substrate (see definition 2.1).

[0031]3.14 Water rinse (container holding sufficient water to completelyimmerse the substrate).

[0032]3.15 Oxidation container (container holding sufficient hydrogenperoxide solution, 10% to completely immerse the substrate).

[0033]3.16 Hydrogen peroxide (any concentration at or above 10%).

[0034]3.17 Plating bath storage bottles (glass 1 liter).

[0035]3.18 Sulfuric acid container (container holding sufficientsulfuric acid solution, 10%, to completely immerse the substrate).

[0036]3.19 Sulfuric acid (any concentration at or above 10%).

[0037]3.20 10% sulfuric acid storage bottle (glass 1 liter).

[0038]3.21 10% hydrogen peroxide storage bottle (glass 1 liter).

[0039]3.22 Graduated cylinder (plastic 100 ml capacity).

[0040]4.0 Plating Bath Preparation

[0041]4.1 Place the plating tank (3.4) on the magnetic stirring plate(3.2) and place the magnetic spin bar (3.3) inside the plating tank.

[0042]4.2 Add 2.0 liters of distilled water (3.6) to the plating tankand turn on the magnetic stirring plate. Set the speed indicator to “5”.

[0043]4.3 Using the laboratory scale (3.1) weight out 200 grams ofmanganese sulfate (3.7) and gradually add it to the water in the platingtank.

[0044]4.4 When all of the manganese sulfate has been dissolved, weighout and gradually add 150 grams of ammonium sulfate (3.8) to thesolution in the plating tank.

[0045]4.5 When all of the ammonium sulfate has been dissolved weigh outand gradually add 60 grams EDTA (3.9).

[0046]4.6 When all of the EDTA has been dissolved, add additionaldistilled water so that the total volume of the plating solution fillsthe plating tank to ½ inch from the top of the tank.

[0047]4.7 The plating bath will have a red or pink tint when freshlymixed but will soon clear and assume a gold tint as plating continues.An insoluble white precipitate will form from the fresh solution andsettle out. This precipitate can be removed from the plating bath bydecanting the clear bath after the precipitant has settled.

[0048]5.0 Plating Procedure

[0049]5.1 With the plating bath in the plating tank, place the platingbath heater (3.5) in the plating tank and turn it on. Adjust the heaterso the bath temperature is maintained at 40° C.

[0050]5.2 Substrate (3.13) is cleaned by polishing with steel wool andscrubbing with a cloth or paper towel and soap and water. Don't touchthe substrate with uncovered fingers after rinsing.

[0051]5.3 Fill the sulfuric acid container (3.18) with sufficientsulfuric acid (3.19) solution (10%) to allow immersion of the substrate.

[0052] Solution: A 10% sulfuric acid solution is used to reduce (removeoxygen from) the surface of the substrate. The 10% acid solution can beprepared from acid concentration of greater than 10% by dilution withdistilled water. An example of dilution follows: Using 60% sulfuricacid, make a 10% solution. Measure out 100 ml of 60% acid using agraduated cylinder. This volume of acid solution contains 60 ML of puresulfuric acid and 50 ml of water. Using the following equation solve for“x” the volume of water to mix with the 60% acid solution:$\frac{{Volume}\quad {of}\quad {pure}\quad {acid}}{{{Volume}\quad {of}\quad {acid}\quad {solution}}\quad + X} = {.10}$$\frac{60\quad {ml}}{{100\quad {ml}} + {X\quad {ml}}} = {.10}$$\frac{60\quad {ml}}{.10} = {100 + X}$ 600 − 100 = X = 500  ml

[0053]  Measure out 500 ml of distilled water and place it in thesulfuric acid container. Add the 100 ml of 60% sulfuric acid slowlywhile mixing. Never add water to acid, always add acid (AAA) to water.The 10% acid solution may be stored in a glass storage bottle (3.20)when not in use. The acid solution is used at room temperature.

[0054]5.4 Immerse the substrate in the sulfuric acid solution for 2 to 5minutes.

[0055]5.5 Rinse the substrate in a running stream of water for 1 minute.Do not dry the substrate or touch it with uncovered fingers afterrinsing.

[0056]5.6 Connect the electrical leads (3.11) to the power supply (3.12)and connect the positive (+) electrical lead to a manganese rod or plate(3.10). Additional anodes, arranged symmetrically around the substrate,can be used to improve the uniformity of the coating. Connect thenegative lead (−) to the substrate (3.13).

[0057]5.7 Set the power supply output to the desired current and placethe rod (anode) and substrate (cathode) into the plating tank. Theelectrical lead end of the anode should not contact the plating bath asthis might cause contamination. The electrical lead end of the cathodecan be in the plating bath as it will just be coated with manganese. SeeFIG. 1.

[0058] Current: Desired plating current will vary directly with theamount of substrate surface area. A ratio can be defined which expressesthe relationship of current to surface area. This ratio is called thecurrent density and has units of amps/area where the area is in units ofsquare inches or square meters. The current density is a constant of theplating process and is used to calculate the desired current for anysize substrate.

[0059] Experiments indicate that a current density of 1.25 amps/squareinch works very well for this process. An example calcution of thedesired plating current for a substrate follows: Calculate the desiredplating current for a copper rod 0.125 inches in diameter and 11 inchesin length.

[0060] The surface area of the rod is: (0.125 in.) (3.14) (11 in.)=4.32square inches

[0061] The desired plating current is: (4.32 sq. in.) (1.25 amps/sq.In.)=5.4 amps

[0062]5.8 Turn on the power supply for the desired amount of time. Itwill be observed that gas is liberated at both the anode and cathode.These gases are hydrogen (at the cathode) and oxygen (at the anode).They are not toxic but being mixed above the plating tank produces acondition of possible combustion so care must be taken not to ignitethem (no smoking, open flame, or sparks in the vicinity).

[0063] Time: Desired plating time will vary with the desired coatingthickness. Using the current density indicated in note 2, a uniform thincoating can be obtained in 1 minute. Plating for 5 minutes will resultin an intermediate thickness while plating for 10 to 15 minutes willgive a thick metal coating to the substrate.

[0064]5.9 After plating is complete, remove the substrate from theplating bath and immerse it in the water rinse (3.14) then turn off thepower supply. This sequence preserves the metal coating from degradationby the plating bath. The bath will attack manganese metal, using themetal ion to replace the ammonium ion in solution. The anode rod shouldalso be removed from the solution when the power is off.

[0065]6.0 Storage

[0066]6.1 The plating bath can be stored and reused many times as themanganese will be replenished in solution by the manganese anodes. Someprecipitate will form during plating and this will settle out ofsolution during storage.

[0067]6.2 Store the plating bath storage bottles (3.17) when it is notused. The shelf life of the plating bath should be unlimited. Adddistilled water if necessary to make up for evaporation anddecomposition of water during plating.

[0068]7.0 Oxidation Procedure

[0069]7.1 Fill the oxidation container (3.15) with sufficient hydrogenperoxide (3.16) solution (10%) to allow immersion of the coatedsubstrate.

[0070] Solution: A 10% hydrogen peroxide solution is used to oxidize themanganese coating on the substrates. The 10% hydrogen peroxide solutioncan be prepared from hydrogen peroxide concentrations of greater than10% by dilution with distilled water. The dilution of a hydrogenperoxide solution follows exactly the procedure used for the dilution ofa sulfuric acid solution explained in section 5.10. The only differencebeing that the sulfuric acid is replaced by hydrogen peroxide. Thehydrogen peroxide solution is used at room temperature.

[0071]7.2 Immerse the coated substrate in the hydrogen peroxide solutionfor 20 minutes. Oxygen gas will be liberated during this process so careshould be taken to remove all sources of ignition from the vicinity.

[0072]7.3 Rinse the coated substrate in water to remove all hydrogenperoxide solution. A running stream of water or the water rinse (3.14)may be used.

[0073]8.0 Safety

[0074]8.1 Good chemical safety procedures should be used at all times inthis process as it involves the use of hazardous materials.

What is claimed as invention is:
 1. A method for reducing ozone outputfrom ion wind devices, said method comprising the steps of: providing anemitter; providing a plurality of collectors, plating said collectorswith a substance adapted to react with ozone to form oxygen; andpositioning said collectors generally equidistant from said emitter inan ion wind device, wherein when the ion wind device operates, saidsubstance reacts with ozone to form oxygen and reduce ozone output. 2.The method of claim 1 wherein said step of plating said collectorscomprises plating with manganese dioxide.
 3. The method of claim 2wherein said step of plating said collectors comprises: providing aplating tank filled with a solution of manganese sulfate and ammoniumsulfate in distilled water; providing a power supply having a positivelead and a negative lead; connecting said negative lead to a collectorto form a cathode, and connecting said positive lead to a manganeseplate to form an anode; placing said cathode and anode in said solution;and energizing said power supply to plate said cathode with manganese.4. The method of claim 3 further including the step of oxidizing saidmanganese plating.
 5. The method of claim 1 wherein said step of platingsaid collectors comprises plating with a precious metal material.
 6. Themethod of claim 1 wherein said step of plating said collectors comprisesplating with activated carbon.
 7. An ion wind device comprising: anemitter; a plurality of collectors positioned generally equidistant fromsaid emitter, said collectors at least partially coated with a substanceadapted to react with ozone to form oxygen, whereby when the ion winddevice operates, said substance reacts with ozone to form oxygen andreduce ozone output.
 8. The ion wind device of claim 7 wherein saidsubstance comprises manganese dioxide.
 9. The ion wind device of claim 7wherein said substance comprises a precious metal.
 10. The ion winddevice of claim 7 wherein said substance comprises activated carbon.